Stabilize and improve cars-rest perf suite

Stabilize and improve cars-rest perf suite

- use a more strict prompt for checking when test tool is
  done. Some 500 error responses (which are ok when leaders
  are down) gave a > prompt which was being wrongly interpreted
  as the system prompt. now, making it look for ~]> instead.

- running the suites twice now, so we can see ask based and
  tell based protocols

- making the python client retry on 500 errors which can come
  when leaders are down and we have askTimeouts

- polling a little longer on some steps

Change-Id: I426f1b03f2fdd3258a39c03bd8e568f16beebf88
Signed-off-by: Jamo Luhrsen <jluhrsen@redhat.com>